VersaTune User Forum

I cleaned the MAF sensor with CRC cleaner and reset the ECU. Actual AFR readings show random peaks in lambda up to 2.0!! i even had some random peaks at 2.0 before cleaning and reseting the ECU. How this is possible? there is no LEAN code error in the diag.


Could you please have a look at the log?

The lambda 2.0 values happened after you accelerated and then left off the throttle.
What intake do you have and what is your current MAF calibration? Ideally you should have logged the MAF g/s values as welll. Also, you can remove the short therm fuel trims for the secondary sensor, they are useless in the case of a MAF calibration.

Yes, lambda 2.0 is when i let it go!

There's a 3inch MAF pipe connected to stock throttle body tube. I just started with Versatuner. My car has already been flashed by previous owner ( unknown tune). I want to overwrite and use Versatuner maps but i want to make sure the MAF readings are correct or i have to get a new sensor.

I recorded a new log.

Thanks for your help

The MAF sensor readings seem to be correct, it's just the calibration in the tune that it's quite a bit off.
The MAF pipe may be 3" external diameter, but internal diameter is not that different than stock, just a tad bigger, probably one of those 2.7" pipes that are flying around as 3".
By how this looks the existing tune seems to have the factory MAF calibration and the car is adjusting 10-12% for it. By example in the factory tune for the MAF voltage of 1.326V corresponds a value of 3.849 g/s of air. In your case at about the same voltage we can see in the logging around 4.21-4.24g/s of air which is an increase of around 9-10%.
So for now I'd install versatuner, download an existing tune and modify it with the MAF calibration values multiplied by 1.09 or 1.1 across the entire board (select all with CTRL+a, and use the X multiplier option in the tool bar).

Ok thanks! I'll start with "Base oct98 with calibration for 3inch MAF sensor" and multiply it by 1.09!! do i need Full license or Lite is enough?

I thought I mentioned stock/factory MAF calibration multiplied by 1.09-1.1 You do NOT have a 3" intake.
And yes you will need a full license for that, you cannot edit maps with the Lite license, nor you can flash tunes made that anybody else than the Versatuner approved tuners..

Thanks! Ok i do it! how about the fuel trims? they look ok?

Kind of, but with the above instructions you will re-do your MAF calibration and only after you flash a map with that change we can discuss again about the fuel trims.
At this point I strongly suggest to contact a professional tuner and get your tune done properly.

Hi

I bought the full license and tried MAF calibration. This is the data after driving 150 km. LTFT is between -0.8% to +8.6%! i still need to multiply the MAF table with 1.0XXX ?

Yeah, more like 1.04 rather than 1.09. You may eventually get to 1.09 but making smaller steps is better, maybe it's not necessary to go as high as 1.09 since even on the lines with 8.x LTFT the STFTs are negative 2-3-4.

The + in the LTFTs come from both the oxygenated fuel additives (mainly ethanol) and from the slightly larger MAF housing, but the loss of smoothness in the MAF curve progression comes from the oxygen in fuel.